Mobile wireless electronic devices are becoming increasingly popular. For example, mobile telephones, portable computers, personal digital assistants (PDAs), portable media players and portable gaming devices are now in wide-spread use. In addition, the features associated with certain types of electronic devices have become increasingly diverse. To name a few examples, many electronic devices have cameras, text messaging capability, Internet browsing capability, electronic mail capability, video playback capability, audio playback capability, image display capability and handsfree headset interfaces.
Many mobile wireless electronic devices have keyboards (also sometimes referred to as keypads) that are used to input information, e.g., telephone numbers, names of contacts, email addresses, Internet websites, addresses, domain names, etc., alphanumeric text, and so on. Two exemplary keyboards are those with one or more keys (sometimes referred to as buttons) and those formed by areas of a touch sensitive display on which indicia, e.g., alphanumeric letters, numbers and symbols may be displayed. Circuitry of such keyboards may be arranged in a matrix format, e.g., a two dimensional matrix of x rows and y columns.
To avoid interfering with antenna functions of mobile wireless electronic devices, inductors have been used to decouple keys of the keyboard from the antenna. Inductors are relatively expensive, which is a disadvantage to using them in such electronic devices.
Electrostatic discharge (ESD) devices have been used to protect circuitry in electronic devices. ESD devices have capacitance, which may increase time required for circuits of the electronic device to stabilize due to resistance capacitance (RC) time constants. Relatively inexpensive ESD devices tend to have relatively large capacitance and, thus, increase such time constant. In contrast, relatively lower capacitance ESD devices reduce such time constants but disadvantageously are more expensive than the relatively higher capacitance ESD devices.
Time consuming methods have been used in the past to determine which key(s) are pressed, as it has been necessary to allow adequate time for circuitry to stabilize due to RC circuit time constants. Those methods consume processor operational time such that the processor is unavailable for other functions or to carry out other functions and also may waste power while the circuitry is in a sense actively waiting for circuitry to stabilize. Also, ghosting or the sensing of a ghost key, e.g., the false appearance of a key being pressed when the key is not being pressed, may occur if adequate time is not provided for circuit components of a mobile wireless electronic device to stabilize.